Shapes of the uterine cavity are different in women with polycystic ovary syndrome

Abstract Purpose A cross‐sectional study was conducted to evaluate differences in uterine morphology between women with or without polycystic ovary syndrome. Methods The authors recruited 333 infertile reproductive‐age women including 93 with polycystic ovary syndrome diagnosed using the criteria of the Japanese Society of Obstetrics Gynecology‐2007. Shapes of uterine cavity were measured by transvaginal three‐dimensional ultrasound. Results The polycystic ovary syndrome group had a significantly deeper indentation (2.2 ± 0.4 mm vs. 0.0 ± 0.2 mm, p < 0.0001) and a significantly more acute indentation angle (162.9 ± 2.2 deg vs. 175.2 ± 1.3 deg, p < 0.0001) than the control group. Conclusion The depth and the apical angle of fundal indentation of uterine cavity are different in women with polycystic ovary syndrome.

examinations without any additional interventions. Venous blood samples for assaying the basal serum concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol, and testosterone were collected during the first 5 days of spontaneous menstrual cycles or if the United States did not show large follicles (diameter > 9 mm) or a thick endometrium (>6 mm). Testing of blood samples was carried out in our laboratory using an Access 2 immunoassay system (Beckman-Coulter). The diagnosis of PCOS was based on the criteria of the Japanese Society of Obstetrics and Gynecology (JSOG)-2007. 12 Briefly, patients who had both oligo-anovulation and polycystic ovarian morphology (PCOM), and either hyperandrogenemia (total testosterone level > 0.47 ng/ dL) or elevated serum LH (>7 mIU/mL) with normal serum FSH (3-8 mIU/mL), were diagnosed as PCOS. Patients with an elevated FSH level (>14 mIU/ml), or who had US-visible tumorous lesions in a small pelvic cavity (e.g., fibroids, endometrial polyps, ovarian cysts, ovarian endometrioma, or adenomyosis), or had a history of uterine surgery (e.g., myomectomy or cesarean section), were excluded.
Transvaginal ultrasound was performed using an 3D-US system (Voluson SWIFT; GE Healthcare Ultrasound) with volumetric transvaginal probes (RIC5-9A-RS) at the time when endometrial thickness was greater than 6 mm regardless of the day of the cycle. The 3D-US datasets of each uterus were anonymized, except for each patient's identification number (ID), and stored for later measurements.

| Measurements of the uterine cavity
To minimize bias in measurement, measurements of uterine shapes were done collectively on stored anonymous 3D-US datasets. We measured the uterine cavity shape on an accurate coronal plane, which was obtained by tracing the exact mid-endometrial line on the touch-panel screen of the 3D-US system ( Figure 1). The tubal ostial line (that connecting the tubal ostium of each side of the uterus) was used as a reference baseline ( Figure 2). Using the "Distance 2 Line" mode of the 3D-US system, used to measure the distance between two parallel lines, the distance between the tubal ostial line and each of the following parallel lines were measured in mm in the following

| Statistical analysis
We designed this study to have an alpha value of 0.05 and a power of 80% to detect 1 mm difference in values of ultrasound F I G U R E 1 Example image obtained by 3D ultrasound system with volumetric transvaginal probes. Left: the midendometrial line traced on a sagittal plane. Right: measures referring the line connecting the tubal ostium (indicated as yellow crosses) of each side of the uterus on a generated coronal plane. measurements between the groups. We calculated that at least a total of 372 subjects would need to be recorded, assuming that standard deviation of the length of uterine cavity in each group would be 3 mm, and 30% would be excluded by exclusion criteria.
To compare the means across groups, Student's t-test and analysis of variance (ANOVA) were used. Statistical analyses were carried out using JMP software (v. 15.2.1; SAS Institute Inc.). Data are represented as mean ± standard error (SE) for continuous variables.
All tests were two-tailed, and p < 0.05 was considered statistically significant.

| RE SULTS
Among 446 patients diagnosed with infertility who visited our clinic, 333 women who met the inclusion criteria were enrolled.
Ninety-three women were diagnosed with PCOS (the PCOS group), and other 240 women were not (the non-PCOS group). In the PCOS group, means of basal LH levels and testosterone levels were significantly higher and means of FSH levels were significantly lower. Means of age, body mass index (BMI), and serum levels of estradiol were not different between the two groups ( Table 1).
The length of cavity and half-width of cavity were not different between the groups. Myometrial thickness was significantly thinner in the PCOS group. The fundal cleft was observed in only one patient with PCOS; therefore, we excluded the indentation depth of the fundal cleft from the analysis. The PCOS group had a significantly deeper indentation and a significantly more acute angle of indentation as compared with the non-PCOS group. Septate uteri were found in three patients only in the PCOS group ( Table 2). The average shape of the uterine cavity of the PCOS group generated  by the mean position of the tubal ostia and the mean depth of cavity indentation resembled an arcuate uterus (Figure 3).

| DISCUSS ION
The etiology of PCOS is still not well understood because of its heterogeneity and complexity. Although genome-wide association studies (GWAS) have found 21 genetic loci associated with PCOS, 14-16 the genetic susceptibility only accounts for less than 10% of its heritability. 17 Tata et al. 2   Rotterdam criteria. 18 Referring to the phenotype classification TA B L E 2 Uterine shapes of the polycystic ovary syndrome (PCOS) and non-PCOS groups.    28 Thus, it appears that prenatal androgen exposure in the first to early second trimester of pregnancy is possibly involved in the origin of uterine anomalies in women with PCOS.

| CON CLUS IONS
These women with PCOS had deeper indentations of the uterine cavity and were more likely to develop an arcuate or septate uterus than were infertile women without PCOS. To our knowledge, this is the first study showing differences in uterine cavity shape in women with PCOS, independent from the diagnostic criteria or standard classifications of uterine anomalies. Limitations of this observational study are that the subjects comprise only women with infertility varying ages and that the evidence for prenatal androgen exposure is missing. However, it was estimated that women with PCOS had deeper indentation of the uterine cavity and were more likely to develop an arcuate or septate uterus. These findings might support evidence for the fetal origin of PCOS. Further prospective cohort studies are required to investigate the relationship between shapes of uterine cavity and other clues to assess prenatal androgen: the AGD or any information of mothers' menstrual or obstetrical history. Above all, further research to reveal the mechanism for the development of Müllerian anomalies in PCOS is essential in this field.

ACK N OWLED G M ENTS
We thank James M. Cummins, PhD from Edanz (https://jp.edanz. com/ac) for editing a draft of this manuscript.

FU N D I N G I N FO R M ATI O N
There was no funding for the project.